trails and better missile origin

src/utils/trail.rs

@@ -10,16 +10,20 @@ pub struct Trail {
 }
 
 impl Trail {
-    pub fn new(pos: Vec3, col_start: LinearRgba, col_end: LinearRgba) -> Self {
-        let mut v = Vec::with_capacity(12);
-        v.push(pos);
+    pub fn new(points: usize, col_start: LinearRgba, col_end: LinearRgba) -> Self {
         Self {
-            points: v,
+            points: Vec::with_capacity(points),
             col_start,
             col_end,
         }
     }
 
+    pub fn with_pos(self, pos: Vec3) -> Self {
+        let mut trail = self;
+        trail.add(pos);
+        trail
+    }
+
     pub fn add(&mut self, pos: Vec3) {
         if self.points.len() >= self.points.capacity() {
             self.points.pop();
@@ -36,19 +40,21 @@ pub fn plugin(app: &mut App) {
 }
 
 fn update_trail(
-    mut query: Query<(&mut Trail, &Gizmo, &GlobalTransform, &ChildOf)>,
+    mut query: Query<(Entity, &mut Trail, &Gizmo, &GlobalTransform)>,
     global_transform: Query<&GlobalTransform>,
     mut gizmo_assets: ResMut<Assets<GizmoAsset>>,
-) -> Result<(), BevyError> {
-    for (mut trail, gizmo, pos, parent) in query.iter_mut() {
+) -> Result {
+    for (e, mut trail, gizmo, pos) in query.iter_mut() {
         trail.add(pos.translation());
 
-        let parent_transform = global_transform.get(parent.parent())?;
+        let parent_transform = global_transform.get(e)?;
 
         let Some(gizmo) = gizmo_assets.get_mut(gizmo.handle.id()) else {
             continue;
         };
 
+        gizmo.clear();
+
         let lerp_denom = trail.points.len() as f32;
         for (i, window) in trail.points.windows(2).enumerate() {
             let [a, b] = window else {